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Monograph: Evening Primrose Oil

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Vitamin E is an optional medicinal ingredient in evening primrose oil products. However, no use or purpose statements may be associated with vitamin E. See Appendix 1 for vitamin E proper name, common name, source material, and dose information.

Date: 2018-09-25


Evening Primrose Oil (Germplasm Resources Information Network Taxonomy)

Proper Name(s)

Common Name(s)

Evening Primrose Oil

Source Material

Route Of Administration


Dosage Form(s)

Use(s) or Purpose(s)

Statement(s) to the effect of:


Duration of use

No statement is required

Risk Information

Statement(s) to the effect of:

Caution(s) and Warning(s):
No statement is required

No statement is required

Known Adverse Reaction(s):
No statement is required

Non-medicinal ingredients

  • Must be chosen from the current Natural Health Products Ingredients Database and must meet the limitations outlined in the database.
  • For products providing vitamin E at doses lower than the minima specified in Table 2 of Appendix 1, vitamin E must be declared as a non-medicinal ingredient


  • The finished product specifications must be established in accordance with the requirements described in the NHPD Quality of Natural Health Products Guide.
  • The medicinal ingredient must comply with the requirements outlined in the Natural Health Products Ingredient Database (NHPID).
  • The medicinal ingredient may comply with the specifications outlined in the Refined Evening Primrose Oil Monograph published in the British Pharmacopoeia or the Evening Primrose Oil, Refined Monograph published in the European Pharmacopoeia. For products indicating one or more of the optional potencies listed in the dose section, an assay must be performed in order to confirm the potency(ies).

References cited

  • European Pharmacopoeia, 6th edition. Strasbourg (France): Directorate for the Quality of Medicines and HealthCare of the Council of Europe (EDQM).; 2008
  • IOM 2003: Institute of Medicine. Committee on Food Chemicals Codex, Food and Nutrition Board, Institute of Medicine. Food Chemicals Codex, 5th edition. Washington (DC): National Academies Press; 2003.
  • IOM 2006: Institute of Medicine. Otten JJ, Pitzi Hellwig J, Meyers LD, editors. Institute of Medicine. Dietary Reference Intakes: The Essential Guide to Nutrient Requirements. Washington (DC): National Academies Press; 2006.
  • Keen H, Payan J, Allawi J, Walker J, Jamal GA, Weir AI, Henderson LM, Bissessar EA, Watkins PJ, Sampson M, Gale EA, Scarpello J, Boddie HG, Hardy KJ, Thomas PK, Misra P, Halonen JP. Treatment of diabetic neuropathy with gamma-linolenic acid. Diabetes Care 1993;16(1):8-15.
  • McGuffin M, Kartesz JT, Leung AY, Tucker AO, editors. 2000. Herbs of Commerce, 2nd edition. Austin(TX): American Herbal Products Association.
  • Mills S, Bone K. 2005. The Essential Guide to Herbal Safety. St. Louis (MO): Elsevier Churchill Livingstone.
  • O'Neil MJ, Smith A, Heckelman PE, Budavari S, editors. The Merck Index: An Encyclopedia of Chemicals, Drugs, and Biologicals, 13th edition. Whitehouse Station (NJ): Merck & Co., Inc.; 2001.
  • Sweetman SC , editor. Martindale: The Complete Drug Reference, 35th edition. London (UK): Pharmaceutical Press; 2007.
  • USDA 2008: ARS, National Genetic Resources Program. Germplasm Resources Information Network (GRIN). National Germplasm Resources Laboratory, Beltsville (MD). [Accessed 2008-01-21]. Available at
  • WHO 2002: World Health Organization (WHO) Monographs on Selected Medicinal Plants, Volume 2. Geneva (CHE): World Health Organization.

References reviewed

  • Barnes J, Anderson LA, Philipson JD. 2007. Herbal Medicines, 3rd edition. London (GB): Pharmaceutical Press.
  • Berardi RR, DeSimone EM, Newton GD, Oszko MA, Popovich NG, Rollins CJ, Shimp LA, Tietze KJ, editors. Handbook of Nonprescription Drugs: An Interactive Approach to Self-Care, 13th edition. Washington (DC): American Pharmaceutical Association; 2002.
  • BP 2008: British Pharmacopoeia, Volume 1. Londron (UK): British Pharmacopoeia Commission. The Stationary Office.
  • Brinker F. 2001. Herb Contraindications and Drug Interactions, 3rd edition. Sandy (OR): Eclectic Medical Publications.
  • Guivernau N, Meza N, Barja P, Roman O. Clinical and experimental study on the long-term effect of dietary gamma-linolenic acid on plasma lipids, platelet aggregation, thromboxane formation, and prostacyclin production. Prostaglandins, Leukotrienes, and Essential Fatty Acids 1994;51(5):311-316.
  • Hoffmann D. 2003. Medical Herbalism: The Science and Practice of Herbal Medicine. Rochester (VT): Healing Arts Press.
  • IOM 2002: Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. Food and Nutrition Board, Institute of Medicine. Washington (DC): National Academy Press; 2002.
  • Lovell CR, Burton JL, Horrobin DF. Treatment of atopic eczema with evening primrose oil [letter]. Lancet 1981;1(8214):278.
  • Manku MS, Horrobin DF, Morse N, Kyte Vicki, Jenkins K. Reduced levels of prostaglandin precursors in the blood of atopic patients: defective delta-6-desaturase function as a biochemical basis for atopy. Prostaglandins Leukotrienes and Medicine 1982;9:615-628.
  • Manku MS, Horrobin DF, Morse NL, Wright S, Burton JL. Essential fatty acids in the plasma phospholipids of patients with atopic eczema. The British Journal of Dermatology 1984;110(6):8-643.
  • McFayden IJ, Forrest AP, Chetty U. Cyclical breast pain - some observations and the difficulties in treatment. The British Journal Clinical Practice 1992;46(3):161-164.
  • McGregor L, Smith AD, Sidey M, Belin J, Zilkha KJ, McGregor JL. Effects of dietary linoleic acid and gamma linolenic acid on platelets of patients with multiple sclerosis. Acta Neurologica Scandinavica 1989;80(1):23-27.
  • McGuffin M, Hobbs C, Upton R, Goldberg A, editors. 1997. American Herbal Products Association's Botanical Safety Handbook. Boca Raton (FL): CRC Press.
  • Mills S, Bone K. 2000. Principles and Practice of Phytotherapy. Toronto (ON): Churchill Livingstone.
  • Morse NL, Clough PM. A meta-analysis of randomized, placebo-controlled clinical trials of efamol evening primrose oil in atopic eczema. Where do we go from here in light of more recent discoveries? Current Pharmaceutical Biotechnology 2006;7(6):24-503.
  • Morse PF, Horrobin DF, Manku MS, Stewart JC, Allen R, Littlewood S, Wright S, Burton J, Gould DJ, Holt PJ, Jansen CT, Mattila L, Meigel W, Dettke TH, Wexler D, Guenther L, Bordoni A, Patrizi A. Meta-analysis of placebo-controlled studies of the efficacy of epogam in the treatment of atopic eczema. Relationship between plasma essential fatty acid changes and clinical response. The British Journal of Dermatology 1989;121(1):75-90.
  • Ockerman P, Bachrack I, Glans S, Rassner S. Evening primrose oil as a treatment of premenstrual syndrome. Recent Advances in Clinical Nutrition 1986;2:405-404.
  • Oliwiecki S, Armstrong J, Burton J, Bradfield J. The effect of essential fatty acids on epidermal atrophy due to topical steroids. Clinical and Experimental Dermatology 1993;18(4):8-326.
  • Oliwiecki S, Burton J. Evening primrose oil and marine oil in the treatment of psoriasis. Clinical and Experimental Dermatology 1994;19(2):9-127.
  • Pashby NL, Mansel RE, Hughes LE, Hanslip J, Preece PE. A clinical trial of evening primrose oil in mastalgia. The British Journal of Surgery 1981;68:801.
  • Puolakka J, Mäkäräinen L, Viinikka L, Ylikorkala O. Biochemical and clinical effects of treating the premenstrual syndrome with prostaglandin synthesis precursors. The Journal of Reproductive Medicine 1985;30:149-153.
  • Puri BK. The safety of evening primrose oil in epilepsy. Prostaglandins, Leukotrienes and Essential Fatty Acids 2007;77:101-103.
  • Schalin-Karrila M, Mattila L, Jansen CT, Uotila P. Evening primrose oil in the treatment of atopic eczema: effect on clinical status, plasma phospholipid fatty acids and circulating blood prostaglandins. The British Journal of Dermatology 1987;117(1):11-19.
  • Schäfer L, Kragballe K. Supplementation with evening primrose oil in atopic dermatitis: effect on fatty acids in neutrophils and epidermis. Lipids 1991;26(7):60-557.
  • Sharpe GR, Farr PM. Evening primrose oil and eczema. Lancet 1990;335:667-668.
  • Shuster J. Black cohosh root? Chasteberry tree? Seizures! Hospital Pharmacy 1996;31:1553-1554.
  • Vaddadi KS. The use of gamma-linolenic acid and linoleic acid to differentiate between temporal lobe epilepsy and schizophrenia. Prostaglandins and Medicine 1981;6:375-379.
  • Van Gool CJ, Zeegers MP, Thijs C. Oral essential fatty acid supplementation in atopic dermatitis - a meta-analysis of placebo-controlled trials. The British Journal of Dermatology 2004;150:728-740.
  • Veale D, Torley H, Richards IM, O'Dowd A, Fitzsimons C, Belch JJ, Sturrock RD. A double-blind placebo controlled trial of Efamol® Marine on skin and joint symptoms of psoriatic arthritis. British Journal of Rheumatology 1994;33(10):8-954.
  • Vericel E, Lagarde M, Mendy F, Courpron PH, Dechavanne M. Effects of gamma-linolenic acid intake on platelet functions in elderly people. Thrombosis Research 1986;42:499-509.
  • Walker T, Singh PK, Wyatt KM, O'Brien PM. The effect of prostanoid precursors and inhibitors on platelet angiotensin II binding. Journal of Obstetrics and Gynaecology 1999;19(1):56-58.
  • Wetzig N. Mastalgia: a 3 year Australian study. The Australian and New Zeland Journal of Surgery 1994;64(5):31-329.
  • Whitaker D, Cilliers J, de Beer C. Evening primrose (Epogam®) in the treatment of chronic hand dermatitis: disappointing therapeutic results. Dermatology 1996;193(2):20-115.
  • Wiersema J, León B. 1999. World Economic Plants: A Standard Reference. Boca Raton (FL): CRC Press LLC.
  • Williamson EM, Evans FJ, Wren RC. Potter's New Cyclopaedia of Botanical Drugs and Preparations. Saffron Walden (GB): C.W. Daniel Company Limited; 1988.
  • Wright S, Burton JL. Oral evening primrose seed oil improves atopic eczema. Lancet 1982; 2(8308):1120-1122.
  • Yoon S, Lee J & Lee S. The therapeutic effect of evening primrose oil in atopic dermatitis patients with dry scaly skin lesions is associated with the normalization of serum gamma-interferon levels. Skin Pharmacology and Applied Skin Physiology 2002;15:20-25.
  • Yoshimoto-Furuie K, Yoshimoto K, Tanaka T, Saima S, Kikuchi Y, Shay J, Horrobin DF, Echizen H. Effects of oral supplementation with evening primrose oil for six weeks on plasma essential fatty acid and uremic skin symptoms in hemodialysis patients. Nephron 1999;91:9-151.

Appendix 1: Vitamin E

Proper name(s), common name(s), and source material(s)

Table 1: Vitamin E proper names, common names and source materials
Proper name (s) Common name(s) Source material(s)

Vitamin E (Sweetman 2007; IOM 2003; O'Neil et al. 2001)

Alpha (α)-tocopherol (Sweetman 2007; O'Neil et al. 2001); Vitamin E (Sweetman 2007; IOM 2003; O'Neil et al. 2001)

All racemic (all rac)-α-tocopherol/ dl-α-tocopherol (Sweetman 2007; IOM 2003)

All rac­-α-tocopheryl acetate/ dl-α-tocopheryl acetate (Sweetman 2007; IOM 2003)

All rac­-α-tocopheryl succinate/ dl-α-tocopheryl acid succinate/ dl-α-tocopheryl succinate (Sweetman 2007)

RRR-α-tocopherol/ d-α-tocopherol (Sweetman 2007; IOM 2003; O'Neil et al. 2001)

RRR-α-tocopheryl acetate/ d-α-tocopheryl
acetate (Sweetman 2007; IOM 2003)

RRR-α-tocopheryl succinate/ d-α-tocopheryl acid succinate/ d-α-tocopheryl succinate (Sweetman 2007; IOM 2003)


The quantity of vitamin E must always be provided in terms of α-tocopherol (AT) (i.e. mg RRR-α-tocopherol), irrespective of the source material used.

IUs may be provided as optional additional information on the PLA form in the "potency" field and on product labels.

Table 2: Dose information for vitamin E presented as dose per day (IOM 2006)
Subpopulation Vitamin E (mg AT/day)
Minimum Maximum
≥ 19 y

Conversion factors:

Table 3: Conversion of vitamin E source material quantity into vitamin E quantity in terms of alpha-tocopherol (AT) and vitamin E activity in terms of International Unit (IU) (IOM 2006)
Source material
(1 mg)
Vitamin E quantity
(mg AT)
Vitamin E activity
RRR-α-Tocopheryl acetate
RRR-α-Tocopheryl succinate
All rac-α-tocopherol
All rac-α-tocopheryl acetate
All rac-α-tocopheryl succinate
Table 4: Conversion of vitamin E source material activity into vitamin E quantity in terms of alpha-tocopherol (AT) (IOM 2006)
Source material
(1 IU)
Vitamin E quantity
(mg AT)
RRR-α-Tocopheryl acetate
RRR-α-Tocopheryl succinate
All rac-α-tocopherol
All rac-α-tocopheryl acetate
All rac-α-tocopheryl succinate

Examples using the vitamin E conversion factors:

  1. Converting vitamin E activity into quantity of AT (mg)

    Convert 400 IU of RRR-α-tocopheryl succinate activity into mg AT:
    = 400 IU x 0.67 mg AT/IU
    = 268 mg AT

  2. Converting vitamin E source material quantity into quantity of AT (mg)

    Convert 200 mg of all rac-α-tocopheryl acetate into mg AT:
    = 200 mg x 0.46 mg AT/mg
    = 92 mg AT